Flexible display device and manufacturing method thereof

ABSTRACT

A flexible display device includes: a flexible substrate having a lower substrate including a prominence pattern, a barrier layer pattern on the prominence pattern, and a planarization film; a gate line on the flexible substrate; a data line crossing the gate line with having a gate insulation film therebetween to define a pixel region; a thin film transistor formed at an intersection of the gate line and the data line; and a passivation layer on the flexible substrate including the thin film transistor. With this configuration, the flexible substrate and the flexible display device can be enhanced by preventing property deterioration of the elements due to bending stresses.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. §119(a) toKorean Patent Application No. 10-2013-0116486 filed on Sep. 30, 2013which is incorporated by reference in its entirety for all purposes asif fully set forth herein.

BACKGROUND

1. Field of the Disclosure

The present application relates to a flexible display device and amanufacturing method thereof. More particularly, the present applicationrelates to a flexible display device which allows elements to be stablyformed on a flexible substrate and enhances flexibility of the flexiblesubstrate and reliability, and to a method of manufacturing the same.

2. Description of the Related Art

Nowadays, the world has seen rapid advances in the electronic displayfield for visually representing an information. As a result, a varietyof flat panel display devices that are slim, light weight, and with lowpower consumption have been developed. Also, the flat panel displaydevices have been rapidly replacing the existing cathode ray tubes(CRTs).

As examples of the flat panel display devices, liquid crystal display(LCD) devices, organic light emitting display (OLED) devices,electrophoretic display (electric paper display (EPD)) devices, plasmadisplay panel device (PDPs), field emission display (FED) devices,electroluminescence display devices (ELDs), elector-wetting display(EWD) devices, and so on have been introduced. Such flat panel displaydevices commonly include a flat display panel, as a necessary component,to display images. The flat display panel is configured with a pair ofcombined substrates which face each other with having an inherent lightemitting or polarizing material layer therebetween.

Also, as the display devices are actively developed, may have enhancedesthetics and provide useful multi-functions to distinguish theproducts. In general, a related art display device includes a flat panelwhich uses a glass substrate. Due to this, it is difficult to diversifythe design. Moreover, because of large flat areas, the related flatpanel devices have a different distance between a main viewing area andits central portion and the main viewing area and its side portion. Inother words, the flat panel designs have a different distance betweenits central portion and its side portion with respect to the mainviewing area.

To address this matter, a flexible display device using a flexiblematerial such as a plastic material and so on is developed. The flexibledisplay device can be curved and designed in a variety of shapes, unlikethe flat panel display devices of the related art. Such a flexibledisplay device can be more attractive as a next generation displaydevice to replace a monitor of a portable computer, an electronicnewspaper, a smart card, and printed media such as books, newspapers,magazines and so on.

To be attractive, the flexible display device must maintain displayperformance when it is bent. However, the flexible display device cancause display defects when bent or curved. This results from the factthat the flexible display device includes multiple thin film layers andelectronic elements which are formed on a flexible substrate. In otherwords, the thin film layers and the electronic elements can be formed bystacking inorganic materials.

When the flexible display device is severely bent or curved, a bendingstress is transferred to the thin film layers and the electronicelements. The bending stress forces the thin film layers to be crackedor deteriorated. Due to this, physical and electrical properties of theelectronic elements can deteriorate.

BRIEF SUMMARY

Accordingly, embodiments of the present application are directed to aflexible display device and a manufacturing method thereof thatsubstantially obviate one or more of problems due to the limitations anddisadvantages of the related art.

The embodiments are to provide a flexible display device which isadapted to enhance flexibility of a flexible substrate and itsflexibility by forming the flexible substrate configured with a lowersubstrate with a prominence pattern and a planarization film, as well amanufacturing method thereof.

Also, the embodiments are to provide a flexible display device and amanufacturing method thereof which are adapted to prevent propertydeterioration of elements and stably form the elements by disposing theelements on a prominence pattern of a lower substrate.

Additional features and advantages of the embodiments will be set forthin the description which follows, and in part will be apparent from thedescription, or may be learned by practice of the embodiments. Theadvantages of the embodiments will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

According to a general aspect of the present embodiment for solving theabove-mentioned problems, a flexible display device includes: a flexiblesubstrate having a lower substrate including a prominence pattern, abarrier layer pattern formed on prominence pattern, and a planarizationfilm; a gate line on the flexible substrate; a data line crossing thegate line with having a gate insulation film therebetween to define apixel region; a thin film transistor at an intersection of the gate lineand the data line; and a passivation layer on the flexible substratecovering the thin film transistor.

A manufacturing method of a flexible display device according to anothergeneral aspect of the present embodiment includes: forming a barrierlayer pattern on a lower substrate; forming a prominence pattern in thelower substrate by etching the lower substrate; forming a planarizationfilm on the lower substrate including the prominence pattern to create aflexible substrate; forming a gate line and a gate electrode on theflexible substrate; forming a gate insulation film on the flexiblesubstrate including the gate line and the gate electrode; forming a thinfilm transistor by sequentially forming a semiconductor layeroverlapping with the gate electrode and a data line and source and drainelectrodes on the gate insulation film; and forming a passivation layeron the flexible substrate including the thin film transistor, whereinthe gate line and the data line cross each other having the gateinsulation film therebetween to define a pixel region.

Other systems, methods, features and advantages will be, or will become,apparent to one with skill in the art upon examination of the followingfigures and detailed description. It is intended that all suchadditional systems, methods, features and advantages be included withinthis description, be within the scope of the present disclosure, and beprotected by the following claims. Nothing in this section should betaken as a limitation on those claims. Further aspects and advantagesare discussed below in conjunction with the embodiments. It is to beunderstood that both the foregoing general description and the followingdetailed description of the present disclosure are exemplary andexplanatory and are intended to provide further explanation of thedisclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the embodiments and are incorporated herein andconstitute a part of this application, illustrate embodiment(s) of thepresent disclosure and together with the description serve to explainthe disclosure. In the drawings:

FIG. 1 is a planar view showing a flexible display device according to afirst exemplary embodiment of the present disclosure;

FIGS. 2A through 2D are cross-sectional views illustrating a method ofmanufacturing a flexible display device according to a second exemplaryembodiment of the present disclosure;

FIGS. 3A and 3B are perspective views showing examples of a flexiblesubstrate in accordance with a third exemplary embodiment of the presentdisclosure;

FIG. 4 is a cross-sectional view showing a flexible display deviceaccording to the first exemplary embodiment of the present disclosure;and

FIG. 5 is a cross-sectional view showing a flexible display deviceaccording to another aspect of the first exemplary embodiment of thepresent disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to embodiments of the presentdisclosure, examples of which are illustrated in the accompanyingdrawings. These embodiments introduced hereinafter are provided asexamples in order to convey their spirits to the ordinary skilled personin the art. Therefore, these embodiments might be embodied in adifferent shape, so are not limited to these embodiments described here.In the drawings, the size, thickness and so on of a device can beexaggerated for convenience of explanation. Wherever possible, the samereference numbers will be used throughout this disclosure including thedrawings to refer to the same or like parts.

FIG. 1 is a planar view showing a flexible display device according toan embodiment of the present disclosure.

Referring to FIG. 1, a flexible display device according to anembodiment of the present disclosure includes a flexible substratedefined into a display area and a non-display area. Also, the flexibledisplay device includes gate lines 111, which are formed in a directionon the flexible substrate, and data line 141 which are formed to crossthe gate lines 111 perpendicularly. The display area of the flexiblesubstrate is defined into a plurality of pixel regions A adjacent towhere the gate lines 111 and the data lines 141 cross each other. Theflexible display device further includes thin film transistors (TFT)formed at the crossing of the gate lines 111 and the data lines 141.Moreover, the flexible display device includes electrode portions 170which are connected to the respective thin film transistor viarespective contact holes.

If the flexible display device according to an embodiment of the presentdisclosure is an LCD device, the electrode portion 170 can be a pixelelectrode. Alternatively, when the flexible display device according toan embodiment of the present disclosure is an OLED device, the electrodeportion 170 can be a first electrode. However, the electrode portion 170is not limited to these cases. The electrode portion 170 can be modifiedand applied in a variety of shapes according to display devices to whichthe flexible display device of the present disclosure is applied.

The thin film transistor includes a gate electrode 110 branched from thegate line 111, and a gate insulation film and a semiconductor layerwhich are stacked on the flexible substrate provided with the gateelectrode 110. Also, the thin film transistor includes a sourceelectrode 140, which is branched from the data line 141 on thesemiconductor layer, and a drain electrode 150 which is separated fromthe source electrode 140 and formed in the same layer as the sourceelectrode 140.

The flexible substrate includes a barrier layer pattern and a prominencepattern which are formed under the thin film transistor. Such a flexiblesubstrate will now be described in detail as follows.

FIGS. 2A through 2D are cross-sectional views illustrating a method ofmanufacturing a flexible display device according to second embodimentof the present disclosure.

Referring to FIG. 2A, a barrier layer pattern 20 may be formed on alower substrate 10. As an example of the lower substrate 10, a plasticthin film, a metal thin film, or others can be used. However, the lowersubstrate 10 is not limited to theses. In other words, the lowersubstrate 10 can be formed from any one of flexible materials differentfrom the above-mentioned materials but suitable for the application.

The barrier layer pattern 20 can be formed from an inorganic material.Actually, the barrier layer pattern 20 can be formed from any oneselected from a material group which includes SiO₂, SiN_(x), SiNO, Ge,and mixtures thereof, but it is not limited to these. The barrier layerpattern 20 can be formed from an opaque inorganic material. In thiscase, the barrier layer pattern 20 can shield light incident to the thinfilm transistor. Particularly, the barrier layer pattern 20 can blockexternal light incident to a channel domain of the semiconductor layerof the thin film transistor. As such, leakage current of the thin filmtransistor can be minimized.

Although it is shown in the drawing that the barrier layer pattern 20 isformed in a single layer structure, the barrier layer pattern 20 can beformed in a multi-layered structure with at least two layers.Preferably, the barrier layer pattern 20 can be formed to include onethrough five layers.

The barrier layer pattern 20 can be formed in a land shape extendingalong the lower substrate 10. Alternatively, the barrier layer pattern20 can be formed in an island shape. In this case, the barrier layerpattern 20 can be formed onto the pixel region (“A” in FIG. 1) too.Preferably, the barrier layer pattern 20 is formed only in an elementregion being occupied by elements, such as the thin film transistor, andso on, which will be formed later.

As shown in FIG. 2B, the lower substrate 10 is partially etched usingthe barrier layer pattern 20 as a mask. Here, the etched lower substrate10 can be formed to include a prominence pattern 11. The prominencepattern 11 can be formed in the same shape as the barrier layer pattern20.

In detail, the prominence pattern 11 can be formed in a land shapeextending along the lower substrate 10. Alternatively, the prominencepattern 11 can be formed in an island shape. In this case, theprominence pattern 11 can be formed up to the pixel region (“A” in FIG.1). Preferably, the prominence pattern 11 is formed only in the elementregion being occupied by elements, such as the thin film transistor, andso on, which will be formed later.

In this manner, the barrier layer pattern 20 and the prominence pattern11 are formed in the element region. Thus, elements formed above theprominence pattern 11 and the barrier layer pattern 20 can be isolatedand stably protected from any physical damage caused by bending stressapplied to a flexible substrate.

In other words, the lower substrate 10 is thinner in all regions exceptthe element region. Therefore, flexibility of the lower substrate 10 canbe enhanced. In general, it is necessary for the flexible display deviceto maintain flexibility. Also, flexibility of the flexible displaydevice depends on flexibility of the flexible substrate. To address thismatter, the lower substrate 10 is thinner in regions (hereinafter,‘non-element regions) not occupied by electrical elements, and allows aflexible substrate with enhanced flexibility and high reliabilityagainst bending stresses.

Referring to FIG. 2C, a planarization film 30 can be coated on the lowersubstrate 10 provided with the prominence pattern 11. The planarizationfilm 30 is used to planarize the lower substrate 10 provided with theprominence pattern 11.

The planarization film 30 can be formed from an organic material. Theorganic material can be one of cytop, olepin, and so on. However, theplanarization film 30 is not limited to these. In other words, theplanarization film 30 can be formed from any material with highductility and suitable for the application.

As shown in FIG. 2D, the planarization film 30 is leveled through aleveling process and compensates for height differences resulting fromthe coating process. A flexible substrate 100 can be prepared throughthe above-mentioned formation procedure. As such, the flexible substrate100 includes the lower substrate 10 which is provided with theprominence pattern 11, the barrier layer pattern 20, and theplanarization film 30.

The planarization film 30 can be formed to have a thicknesscorresponding to the thickness of the prominence pattern 11 plus thethickness of the barrier layer pattern 20. As such, the leveling processcan be performed on the planarization film 30 until only the uppersurface of the barrier layer pattern 20 is exposed.

Subsequently, elements including the thin film transistor, gate and datalines, and so on can be formed on the barrier layer pattern 20 in such amanner as to be in contact with the barrier layer pattern 20. In otherwords, the elements can be formed above the prominence pattern 11 of thelower substrate 10 and the barrier layer pattern 20. As such, theseelements can be more isolated and protected. On the other hand, only thelower substrate 10 and the planarization film 30 exist in thenon-element regions being not occupied by the elements. This flexiblesubstrate 100 will now be explained in more detail as follows.

FIGS. 3A and 3B are perspective views showing examples of a flexiblesubstrate in accordance with a third exemplary embodiment of the presentdisclosure.

FIG. 3A is a perspective view showing a first example of the flexiblesubstrate 200 according to an embodiment of the present disclosure. Theflexible substrate 200 of the first example includes a barrier layerpattern 20 and a prominence pattern 11 which are extended along a lowersubstrate 10.

The barrier layer pattern 20 and the prominence pattern 11 can be formedin the same direction as the data line. Alternatively, the barrier layerpattern 20 and the prominence pattern 11 can be formed in the samedirection as the gate line.

FIG. 3B is a perspective view showing a second example of the flexiblesubstrate 300 according to the third embodiment of the presentdisclosure. The flexible substrate 300 of the second example includes abarrier layer pattern 20 formed in an island shape and a prominencepattern 11 formed in an island shape. The barrier layer pattern 20 andthe prominence pattern 11 which have the island shape can be formed in aregion corresponding to a pixel region. In other words, the islandpattern can be formed in a region corresponding to a pixel region. Assuch, the barrier layer pattern 20 and prominence patter 11 can beformed into the same number as the pixel regions. The barrier layerpattern 20 and the prominence pattern 11 each having the island shapecan be formed only in a part of the pixel region which is occupied by athin film transistor. Electronic elements will be formed on the flexiblesubstrate 100.

FIG. 4 is a cross-sectional view along I-I′ from FIG. 1 showing aflexible display device according to a first embodiment of the presentdisclosure.

As shown in FIG. 4, a gate electrode 110 branched from the gate line isformed on the flexible substrate 400. Also, a gate insulation film 120can be formed on the entire surface of the flexible substrate 400provided with the gate electrode 110.

The gate line and the gate electrode 110 can be formed by stacking atleast one metals and transparent conductive materials in at least onelayer. The metals include molybdenum Mo, titanium Ti, tantalum Ta,tungsten W, copper Cu, chrome Cr, aluminum Al, and alloys thereof. Thetransparent conductive materials include ITO (indium-tin-oxide), IZO(indium-zinc-oxide), and ITZO (indium-tin-zinc-oxide). Although the gateelectrode 110 is formed in a single metal layer as shown in the drawing,it is not limited to this. In other words, the gate electrode 110 can beformed by stacking at least two metal layers.

The gate insulation film 120 can be formed from one of a dielectricmaterial, a high dielectric constant material, and a mixture thereof.The dielectric material can be one of SiO_(x), SiN_(x), SiNO, HfO₂,Al2O₃, Y2O₃, Ta2O₅, and so on. Although the gate insulation film 120 isformed in a single layer as shown in the drawing, it is not limited tothis. In other words, the gate insulation film 120 can be formed in amulti-layered structure with at least two layers.

A semiconductor layer 130 can be formed on the gate insulation film 120in such a manner as to overlap with at least a part of the gateelectrode 110. Also, a data line, a source electrode 140 branched fromthe data line, and a drain electrode 150 separated from the sourceelectrode 140 are formed on the flexible substrate 100 provided with thesemiconductor layer 130. The source electrode 140 and the drainelectrode 150 are partially overlap with the semiconductor layer 130.Then, a passivation layer 160 can be formed on the entire surface of theflexible substrate 400 provided with the source electrode 140 and thedrain electrode 150.

A formation procedure of the data line and the source and drainelectrodes 140 and 150 can be performed after a formation procedure ofthe semiconductor layer 130. Alternatively, the semiconductor layer 130,the data line and the source and drain electrodes 140 and 150 can beformed through a single procedure using a half-tone mask or adiffractive mask. In detail, the semiconductor layer 130, the data lineand the source and drain electrodes 140 and 150 can be formed bysequentially depositing a semiconductor material layer and a metal layerand patterning the metal layer and the semiconductor material layerusing one of the half-tone mask and the diffractive mask.

The method of forming the thin film transistor which includes the gateelectrode 110, the semiconductor layer 130 and the source and drainelectrodes 140 and 150 is not limited to the above-mentioned formationprocedure. Various changes or modifications of the present disclosureare possible without departing from the spirit of the present disclosureas far as the thin film transistor is formed above the prominencepattern 11 of the lower substrate 10 and the barrier layer pattern 20.

The semiconductor layer 130 can be formed from one of a siliconsemiconductor and an oxide semiconductor of A_(x)B_(y)C_(z)O (x, y andz≧0). In A_(x)B_(y)C_(z)O, “A”, “B” and “C” can be selected from Zn, Cd,Ga, In, Sn, Hf, and Zr, respectively. Preferably, the semiconductorlayer 130 can be formed from one of ZnO, InGaZnO₄, ZnInO, ZnSnO,InZnHfO, SnInO, and SnO, but it is not limited to this.

The data line and the source and drain electrodes 140 and 150 can beformed from one of molybdenum Mo, titanium Ti, tantalum Ta, tungsten W,copper Cu, chrome Cr, aluminum Al, and alloys thereof. Alternatively,the data line and the source and drain electrodes 140 and 150 can beformed from one of ITO (indium-tin-oxide), IZO (indium-zinc-oxide,) andITZO (indium-tin-zinc-oxide). Although the data line and the source anddrain electrodes 140 and 150 are formed in a single metal layer as shownin the drawing, they are not limited to this. In other words, the dataline and the source and drain electrodes 140 and 150 can be formed bystacking at least two metal layers.

The thin film transistor including the gate electrode 110, thesemiconductor layer 130 and the source and drain electrodes 140 and 150can be formed above the prominence pattern 11 and the barrier layer 20of the flexible substrate 400. Also, regions of the lower substrate 10being occupied by the prominence pattern 11 and the barrier layerpattern 20 have a higher hardness compared to the other regions of thelower substrate 10. As such, elements including the thin film transistorcan be stably formed.

Also, only the lower substrate 10 with flexibility and the planarizationfilm 30 exist in the non-element regions not occupied by the elements.As such, flexibility of the flexible substrate 400 can be enhanced.Moreover, the elements can be stably formed and flexibility of theflexible display device can be sufficiently secured.

FIG. 5 is a cross-sectional view along I-I′ of FIG. 1 showing a flexibledisplay device according to another aspect of the first embodiment ofthe present disclosure.

Referring to FIG. 5, the flexible display device according to thisaspect of the first embodiment of the present disclosure includes a thinfilm transistor, which is configured with a gate electrode 110, a gateinsulation film, a semiconductor layer 130, a source electrode 140, adrain electrode 150, and a passivation layer. The description of likeelements will be omitted.

After the formation of the passivation layer, a gate insulation pattern220 and a passivation layer pattern 260 can be formed by removing thepassivation layer and the gate insulation film from the remainder of theflexible substrate 400 except the regions of elements, which include thethin film transistor and wirings, through an etching process.Preferably, the gate insulation film pattern 220 and the passivationlayer pattern 260 can be formed by etching the passivation layer and thegate insulation film on boundary regions of the pixel regions throughthe etching process.

In other words, the gate insulation film pattern 220 and the passivationlayer pattern 260 can be formed only in the regions being occupied bythe elements and the wirings. For example, the gate insulation filmpattern 220 and the passivation layer pattern 260 are formed in theregions being occupied by the thin film transistor, the gate line andthe data line.

Since the gate insulation film pattern 220 and the passivation layerpattern 260 are formed by partially etching the passivation layer andthe gate insulation film, the elements including the thin filmtransistor and so on can be formed independently of one another. Assuch, reliability of the flexible display device can be secured. Also,grooves may be formed in the boundaries of the pixel regions. Inaccordance therewith, flexibility of the flexible display device can beenhanced.

As described above, the flexible display device and the manufacturingmethod thereof according to embodiments of the present disclosure allowthe flexible substrate including the lower substrate with the prominencepattern and the planarization film to be formed. As such, flexibility ofthe flexible substrate and the flexible display device can be enhanced.Also, the elements can be formed on the prominence pattern of the lowersubstrate. In accordance therewith, property deterioration of theelements due to bending stresses can be prevented.

Although the present disclosure has been limitedly explained regardingonly the embodiments described above, it should be understood by theordinary skilled person in the art that the present disclosure is notlimited to these embodiments, but rather that various changes ormodifications thereof are possible without departing from the spirit ofthe present disclosure. Accordingly, the scope of the present disclosureshall be determined only by the appended claims and their equivalentswithout being limited to the detailed description.

1-19. (canceled)
 20. A flexible display device comprising: a flexiblesubstrate having a lower substrate including a prominence pattern, abarrier layer on the prominence pattern, and a planarization film; agate line on the flexible substrate; and a data line crossing the gateline to define a pixel region.
 21. The flexible display device of claim20, wherein the prominence pattern is formed in a land shape extendingalong the lower substrate.
 22. The flexible display device of claim 20,wherein the prominence pattern is formed in an island shape.
 23. Theflexible display device of claim 20, wherein the prominence pattern iscorresponds to the pixel region.
 24. The flexible display device ofclaim 20, wherein the thin film transistor is formed on the prominencepattern and the barrier layer pattern.
 25. The flexible display deviceof claim 20, wherein the barrier layer pattern is formed from aninorganic material.
 26. The flexible display device of claim 20, whereinthe planarization film is formed from an organic material.
 27. Theflexible display device of claim 20, wherein the planarization film is asame thickness as the sum of a thickness of the prominence pattern and athickness of the barrier layer pattern.
 28. The flexible display deviceof claim 20, a gate insulation film is disposed between the gate lineand the data line.
 29. The flexible display device of claim 28, a thinfilm transistor at an intersection of the gate line and the data line.30. The flexible display device of claim 29, wherein the gate insulationfilm is patterned only onto elements including the thin film transistorand wirings including the gate line.
 31. The flexible display device ofclaim 30, a passivation layer on the flexible substrate covering thethin film transistor.
 32. The flexible display device of claim 31,wherein the passivation layer is patterned only onto elements includingthe thin film transistor and wirings including the gate line and thedata line.